diff --git a/src/eval/dict.rs b/src/eval/dict.rs
index bf99ea17e..c1c3f5052 100644
--- a/src/eval/dict.rs
+++ b/src/eval/dict.rs
@@ -5,7 +5,7 @@ use std::ops::{Add, AddAssign};
 use std::rc::Rc;
 
 use super::Value;
-use crate::eco::EcoString;
+use crate::util::EcoString;
 
 /// Create a new [`Dict`] from key-value pairs.
 #[macro_export]
@@ -13,7 +13,7 @@ macro_rules! dict {
     ($($key:expr => $value:expr),* $(,)?) => {{
         #[allow(unused_mut)]
         let mut map = std::collections::BTreeMap::new();
-        $(map.insert($crate::eco::EcoString::from($key), $crate::eval::Value::from($value));)*
+        $(map.insert($crate::util::EcoString::from($key), $crate::eval::Value::from($value));)*
         $crate::eval::Dict::from_map(map)
     }};
 }
diff --git a/src/eval/function.rs b/src/eval/function.rs
index daa5ff1e2..ca447a48d 100644
--- a/src/eval/function.rs
+++ b/src/eval/function.rs
@@ -3,7 +3,7 @@ use std::ops::Deref;
 use std::rc::Rc;
 
 use super::{Cast, EvalContext, Value};
-use crate::eco::EcoString;
+use crate::util::EcoString;
 use crate::syntax::{Span, Spanned};
 
 /// An evaluatable function.
diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 5b00819b9..682a3855c 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -26,7 +26,7 @@ use std::path::Path;
 use std::rc::Rc;
 
 use crate::diag::{Diag, DiagSet, Pass};
-use crate::eco::EcoString;
+use crate::util::EcoString;
 use crate::geom::{Angle, Fractional, Length, Relative};
 use crate::image::ImageCache;
 use crate::loading::{FileId, Loader};
diff --git a/src/eval/template.rs b/src/eval/template.rs
index 4d0039982..0be2492be 100644
--- a/src/eval/template.rs
+++ b/src/eval/template.rs
@@ -4,7 +4,7 @@ use std::ops::{Add, Deref};
 use std::rc::Rc;
 
 use super::Value;
-use crate::eco::EcoString;
+use crate::util::EcoString;
 use crate::exec::ExecContext;
 use crate::syntax::{Expr, SyntaxTree};
 
diff --git a/src/eval/value.rs b/src/eval/value.rs
index 4b3cd807e..b7fdcbc21 100644
--- a/src/eval/value.rs
+++ b/src/eval/value.rs
@@ -5,7 +5,7 @@ use std::rc::Rc;
 
 use super::{ops, Array, Dict, Function, Template, TemplateFunc};
 use crate::color::{Color, RgbaColor};
-use crate::eco::EcoString;
+use crate::util::EcoString;
 use crate::exec::ExecContext;
 use crate::geom::{Angle, Fractional, Length, Linear, Relative};
 use crate::syntax::Spanned;
diff --git a/src/exec/context.rs b/src/exec/context.rs
index 725907f22..3a3eb7027 100644
--- a/src/exec/context.rs
+++ b/src/exec/context.rs
@@ -3,7 +3,7 @@ use std::rc::Rc;
 
 use super::{Exec, ExecWithMap, State};
 use crate::diag::{Diag, DiagSet, Pass};
-use crate::eco::EcoString;
+use crate::util::EcoString;
 use crate::eval::{ExprMap, Template};
 use crate::geom::{Align, Dir, Gen, GenAxis, Length, Linear, Sides, Size};
 use crate::layout::{
diff --git a/src/exec/mod.rs b/src/exec/mod.rs
index 8b769def1..ff4faa227 100644
--- a/src/exec/mod.rs
+++ b/src/exec/mod.rs
@@ -9,7 +9,7 @@ pub use state::*;
 use std::fmt::Write;
 
 use crate::diag::Pass;
-use crate::eco::EcoString;
+use crate::util::EcoString;
 use crate::eval::{ExprMap, Template, TemplateFunc, TemplateNode, TemplateTree, Value};
 use crate::geom::{Dir, Gen};
 use crate::layout::{LayoutTree, StackChild, StackNode};
diff --git a/src/layout/incremental.rs b/src/layout/incremental.rs
index cbd553301..352434ede 100644
--- a/src/layout/incremental.rs
+++ b/src/layout/incremental.rs
@@ -269,46 +269,9 @@ impl Constraints {
         let current = regions.current.to_spec();
         let base = regions.base.to_spec();
 
-        self.exact.horizontal.set_if_some(current.horizontal);
-        self.exact.vertical.set_if_some(current.vertical);
-        self.base.horizontal.set_if_some(base.horizontal);
-        self.base.vertical.set_if_some(base.vertical);
-    }
-}
-
-/// Extends length-related options by providing convenience methods for setting
-/// minimum and maximum lengths on them, even if they are `None`.
-pub trait OptionExt {
-    /// Sets `other` as the value if `self` is `None` or if it contains a
-    /// value larger than `other`.
-    fn set_min(&mut self, other: Length);
-
-    /// Sets `other` as the value if `self` is `None` or if it contains a
-    /// value smaller than `other`.
-    fn set_max(&mut self, other: Length);
-
-    /// Sets `other` as the value if `self` is `Some`.
-    fn set_if_some(&mut self, other: Length);
-}
-
-impl OptionExt for Option<Length> {
-    fn set_min(&mut self, other: Length) {
-        match self {
-            Some(x) => x.set_min(other),
-            None => *self = Some(other),
-        }
-    }
-
-    fn set_max(&mut self, other: Length) {
-        match self {
-            Some(x) => x.set_max(other),
-            None => *self = Some(other),
-        }
-    }
-
-    fn set_if_some(&mut self, other: Length) {
-        if self.is_some() {
-            *self = Some(other);
-        }
+        self.exact.horizontal.and_set(Some(current.horizontal));
+        self.exact.vertical.and_set(Some(current.vertical));
+        self.base.horizontal.and_set(Some(base.horizontal));
+        self.base.vertical.and_set(Some(base.vertical));
     }
 }
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 0f88d150e..56e0687a0 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -32,6 +32,7 @@ use std::rc::Rc;
 use crate::font::FontCache;
 use crate::geom::*;
 use crate::image::ImageCache;
+use crate::util::OptionExt;
 use crate::Context;
 
 /// Layout a tree into a collection of frames.
diff --git a/src/layout/par.rs b/src/layout/par.rs
index 56847b9bc..03d7efd56 100644
--- a/src/layout/par.rs
+++ b/src/layout/par.rs
@@ -5,9 +5,8 @@ use unicode_bidi::{BidiInfo, Level};
 use xi_unicode::LineBreakIterator;
 
 use super::*;
-use crate::eco::EcoString;
 use crate::exec::TextState;
-use crate::util::{RangeExt, SliceExt};
+use crate::util::{EcoString, RangeExt, SliceExt};
 
 type Range = std::ops::Range<usize>;
 
diff --git a/src/lib.rs b/src/lib.rs
index 5c4772489..da0063333 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -33,7 +33,6 @@ pub mod diag;
 #[macro_use]
 pub mod eval;
 pub mod color;
-pub mod eco;
 pub mod exec;
 pub mod export;
 pub mod font;
diff --git a/src/library/mod.rs b/src/library/mod.rs
index 3c1d752dd..213106d6f 100644
--- a/src/library/mod.rs
+++ b/src/library/mod.rs
@@ -17,12 +17,12 @@ use std::fmt::{self, Display, Formatter};
 use std::rc::Rc;
 
 use crate::color::{Color, RgbaColor};
-use crate::eco::EcoString;
 use crate::eval::{EvalContext, FuncArgs, Scope, Template, Type, Value};
 use crate::exec::{Exec, FontFamily};
 use crate::font::{FontStyle, FontWeight, VerticalFontMetric};
 use crate::geom::*;
 use crate::syntax::Spanned;
+use crate::util::EcoString;
 
 /// Construct a scope containing all standard library definitions.
 pub fn new() -> Scope {
diff --git a/src/parse/mod.rs b/src/parse/mod.rs
index 38a489b27..a94345a85 100644
--- a/src/parse/mod.rs
+++ b/src/parse/mod.rs
@@ -15,8 +15,8 @@ pub use tokens::*;
 use std::rc::Rc;
 
 use crate::diag::Pass;
-use crate::eco::EcoString;
 use crate::syntax::*;
+use crate::util::EcoString;
 
 /// Parse a string of source code.
 pub fn parse(src: &str) -> Pass<SyntaxTree> {
diff --git a/src/parse/resolve.rs b/src/parse/resolve.rs
index c36762150..f97d53835 100644
--- a/src/parse/resolve.rs
+++ b/src/parse/resolve.rs
@@ -1,6 +1,6 @@
 use super::{is_newline, Scanner};
-use crate::eco::EcoString;
 use crate::syntax::{Ident, RawNode, Span};
+use crate::util::EcoString;
 
 /// Resolve all escape sequences in a string.
 pub fn resolve_string(string: &str) -> EcoString {
diff --git a/src/syntax/ident.rs b/src/syntax/ident.rs
index b1328bbe9..462361a5b 100644
--- a/src/syntax/ident.rs
+++ b/src/syntax/ident.rs
@@ -3,7 +3,7 @@ use std::ops::Deref;
 use unicode_xid::UnicodeXID;
 
 use super::Span;
-use crate::eco::EcoString;
+use crate::util::EcoString;
 
 /// An unicode identifier with a few extra permissible characters.
 ///
diff --git a/src/syntax/mod.rs b/src/syntax/mod.rs
index 895a5bc5d..9a4ca708a 100644
--- a/src/syntax/mod.rs
+++ b/src/syntax/mod.rs
@@ -13,7 +13,7 @@ pub use node::*;
 pub use span::*;
 pub use token::*;
 
-use crate::eco::EcoString;
+use crate::util::EcoString;
 
 /// The abstract syntax tree.
 ///
diff --git a/src/eco.rs b/src/util/eco.rs
similarity index 100%
rename from src/eco.rs
rename to src/util/eco.rs
diff --git a/src/util.rs b/src/util/mod.rs
similarity index 71%
rename from src/util.rs
rename to src/util/mod.rs
index 8a8c04b6d..2c53bc706 100644
--- a/src/util.rs
+++ b/src/util/mod.rs
@@ -1,9 +1,57 @@
 //! Utilities.
 
+mod eco;
+
+pub use eco::EcoString;
+
 use std::cmp::Ordering;
 use std::ops::Range;
 use std::path::{Component, Path, PathBuf};
 
+/// Additional methods for options.
+pub trait OptionExt<T> {
+    /// Replace `self` with `other` if `self` is `Some`.
+    fn and_set(&mut self, other: Option<T>);
+
+    /// Sets `other` as the value if `self` is `None` or if it contains a value
+    /// larger than `other`.
+    fn set_min(&mut self, other: T)
+    where
+        T: Ord;
+
+    /// Sets `other` as the value if `self` is `None` or if it contains a value
+    /// smaller than `other`.
+    fn set_max(&mut self, other: T)
+    where
+        T: Ord;
+}
+
+impl<T> OptionExt<T> for Option<T> {
+    fn and_set(&mut self, other: Option<T>) {
+        if self.is_some() {
+            *self = other;
+        }
+    }
+
+    fn set_min(&mut self, other: T)
+    where
+        T: Ord,
+    {
+        if self.as_ref().map_or(true, |x| other < *x) {
+            *self = Some(other);
+        }
+    }
+
+    fn set_max(&mut self, other: T)
+    where
+        T: Ord,
+    {
+        if self.as_ref().map_or(true, |x| other > *x) {
+            *self = Some(other);
+        }
+    }
+}
+
 /// Additional methods for slices.
 pub trait SliceExt<T> {
     /// Split a slice into consecutive groups with the same key.